Recently, in an indoor unit of an air-conditioning apparatus, it has become a mainstream that the indoor unit employs a design having a flat surface shape without being provided with a bar in a front surface of a front panel so as to blend with an interior's design of a room, resulting in sucking the air through a top of the indoor unit. However, in this no front bar configuration, an amount of the air to be sucked from the top becomes insufficient, because the air cannot be sucked through the front. As a result, the air is required to be taken from the front panel, too. Then, there has been proposed an indoor unit of an air-conditioning apparatus (see, for example, Patent Literature 1) having such a configuration that a horizontal recess is formed in a vertical center of a front panel having a flat surface shape, and that a part of the horizontal recess is formed as an air inlet. With this configuration, the amount of the air to be sucked is increased, a monotonous design of the flat surface is accented, and designing ability is enhanced.
In this case, the front panel is required to be mountable/dismountable and easily handled so as to enable inspection and repair of the indoor unit of an air-conditioning apparatus, or cleaning of an internal filter and the front panel. Accordingly, in a case of the configuration in which the horizontal recess is formed in the vertical center of the front panel formed of a synthetic resin into the flat surface shape, and in which the part of the horizontal recess is formed as the air inlet, a region of the front panel extending from an edge of the air inlet to a right or left end portion is liable to deform and crack due to an external force generated, for example, when the front panel falls down at the time of mounting or dismounting the front panel. Accordingly, in Patent Literature 1, in order to reinforce strength, a bottom surface of the recess at the right or left end portion is shallower than a bottom surface of the recess at a portion excluding the right and left end portions.